Tuesday, January 6, 2015

Lockheed XP-80

24 January 2015 Update: There continue to be questions about the topside color based on close examination of the color photos of the prototype in the Air and Space monograph. However, Dana Bell is of the opinion that it is most likely Army Air Forces Dark OD but possible that it is RAF Dark Green or ANA OD.

19 January 2015 Update: Bob Sikkel noted that the horizontal stabilizer data for the XP-80 and the P-80A were the same so my overlay of the P-80A stab appeared to be incorrect. It turns out that I had used an inaccurate drawing for the overlay. I've revised the top view with one that matches the data.

9 January 2015 Update: Bob Sikkel, who got me interested in this project in the first place, provided the link to another walkaround that provides excellent pictures of the landing gear, among other things: http://aircraftwalkaround.hobbyvista.com/p80/p80.htm 

8 January 2015 Update: It turns out that the color scheme as reported in the monograph that I relied on was incorrect. I've updated the following accordingly.

The Lockheed XP-80 was a one-off prototype powered by a different engine than the P-80A and subsequent Shooting Stars. It was a bit shorter and lighter than the P-80A. This photo was taken in conjunction with the first flight.

The more powerful but heavier engine required rebalancing the airplane by extending the fuselage forward. It probably allowed an increase in internal fuel as well since the main fuel tank was located in the fuselage between the cockpit and the engine.

Gerry Asher, aka Fox Three, described his conversion in the April 2001 issue (Vol 23 No 3) of Scale Aircraft Modeling. I don't think that he had the benefit of the National Air and Space Museum monograph on the P-80 Shooting Star.
The monograph includes a three-view of the XP-80 as well as several pictures, including some of the cockpit and some taken during the restoration process.

The difference in overall length between the XP-80 and the P-80A was 20 inches but the location of the aft end of the tail pipe is not the same for both airplanes so that is only an approximation of the stretch. After closely comparing the XP-80 three-view to those of the production Shooting Stars, I decided that the most accurate way to reduce the length was to remove 20 to 24 inches in two places. (Gerry removed 27 inches and after I drew this illustration, Bob Sikkel used the drawings I had to determine that it was very likely 25 inches.) Note that the XP-80 did not have a pair of speed brakes under the fuselage approximately where the lower section needs to be removed.
Craig Kaston subsequently provided me with some screen shots of photographs of XP-80 drawings that had fuselage station information but a combination of distortion and low resolution didn't allow an exact determination of the stretch. Overlays of the XP-80 fuselage station drawing with an F-80 fuselage station drawing established the stretch as 23 inches, plus or minus an inch; Moreover, there was a pencil notation on the XP-80 drawing at one fuselage station that suggests the increase was 23 inches. However, as noted above, Bob Sikkel's careful evaluation of the XP-80 and production P-80 fuselage stations results in a very likely stretch of 25 inches. (The good news is that two inches in 1/72nd and 1/48th is a little less or more than 1/32 of an inch respectively, which is probably less than the accuracy you can achieve when sectioning and rejoining the parts.)

The XP-80 drawing in the NASM monograph is clearly wrong with respect to the canopy and simplistic with respect to the engine inlet. I've added some other details to it as well based on photographs. Note that although the wells for the main landing gear wheels are in the same location in the wing, when the landing gear is extended, the wheels don't move quite as far aft. The XP-80 main landing gear tires were slightly bigger in diameter (27" versus 26") and appear to be wider.
(The inboard main landing gear doors are shown as the true size; they actually angled outboard and so would appear to be less deep in a three view than as shown above.)

The top view of the XP-80:

The XP-80 was restored by the National Air and Space Museum to the configuration it was in when retired by the Air Force, including markings. Unfortunately, an error was made in determining the color of the upper surfaces.* It had in fact been painted the standard olive drab and light gray of the time, but then polished to minimize drag.
Note that the rounded wing tips and tail were added early on in flight test. A wing leading edge fillet was scabbed on at some point after the first flight. The tailpipe on the restoration also extends farther aft than it did on the airplane at first flight.

The most difficult part of the conversion will be the relocation of the engine inlets forward on the fuselage and and changing the inlet shape to that of the XP-80 configuration.

The sliding canopy, but not the windscreen, was tinted. However, pictures of the aircraft before its first flight do not have the aft end of the canopy standing proud of the fuselage like it does now. (This discrepancy is noted in the NASM monograph.) I suspect that it is not the XP-80's original canopy (some of the first P-80As had tinted sliding canopies as well) and since the prototype was hand built, the replacement doesn't quite fit.

Some detail pictures are provided here: http://www.cybermodeler.com/aircraft/t-33/xp-80_walk.shtml

* Dana Bell: The story had been that as the XP-80 was being completed, the Lockheed paint shop was told to camouflage it. The painter told the NASM project curator they had just been camouflaging Venturas (he actually said Hudsons, though that production had long since been completed) and simply used up the last of the green that was already in the spray gun. The curator decided that the closest equivalent for British Dark Green was US Medium Green - the original color was actually specified to be Dark Olive Drab. The XP-80 was also polished and waxed to lessen wind resistance. Years later, the wax oxidized, as did the underlying paint - the entire upper surface and sides of the aircraft turned a burnt orange, and remained so until restoration. OD will turn brownish orange with age, but Medium Green won't.